The present invention generally relates to improved medical devices and methods for use. More particularly, the present invention relates to a balloon catheter having adjustable capability for positioning and orienting the tip section resulting in more effective radioactive treatment of eccentric atheroma in a patient for use in association with coronary, renal, cerebral, and peripheral angioplasty/stenting.
The primary methods of intervention for coronary artery diseases are coronary artery bypass graft surgery (CABG) and percutaneous transluminal coronary angioplasty (PTCA). In PTCA, a catheter equipped with an inflatable balloon is threaded intravascularly to the site of atherosclerotic narrowing of the vessel. Inflation of the balloon with concomitant compression of atheroma enlarges the atherosclerotic narrowing and enlarges the lumen by stretching the vessel wall. PTCA has emerged as a very effective alternative to CABG. That is, it is less invasive, has lower patient risks, and costs less than CABG.
The principle limitation of angioplasty is restenosis, a re-narrowing of the treated vessel to less than 50% of its original size. Studies have shown that restenosis affects 25-45% of PTCA patients, requiring re-intervention at some point in the first six months post the initial procedure. Stents have proven highly effective at reducing both elastic recoil of the arterial wall and vascular remodeling by holding the vessel open. Restenosis rates after stenting have been reported in the 20-30% ranges due to primarily intimal hyperplasia. Intimal hyperplasia is a physiological response to injury, similar to the scarring that occurs in wound healing. During the first few weeks after angioplasty, cells multiply on the inside of the artery, causing the inner lumen to shrink. Several approaches have been suggested and tried to reduce the restenosis rate with mixed results, including atherectomy, laser, cryo-ablation, thermo-ablation, ultrasound, calcium antagonists, fish oils, steroids, or the like.
Radiation seems to be effective at preventing smooth muscle cell proliferation by breaking the strands of DNA in living cells. One of the current radiation therapies is first to advance a flexible delivery balloon catheter through an artery or a vein of a patient until the distal tip is at or near the lesion region of the treated vessel. Subsequently, a treatment apparatus, comprising a wire or a small catheter having a radiation source at the tip is advanced through the delivery balloon catheter until the radiation source is disposed at the lesion region. The radiation source is held at the lesion region for a predetermined treatment period calculated to deliver an effective radioactive dose of radiation. Thereafter the treatment apparatus and the delivery balloon catheter are then withdrawn.
Hess in U.S. Pat. No. 5,411,466 teaches a method and apparatus for treating restenosis by positioning a radioactive dose to the region after angioplasty to inhibit restenosis. The catheter has at its distal end a radioactive source, wherein the source is maneurable to the site of a lesion allowing the site to be exposed to the radiation dose that will affect smooth muscle cells such that the rapid growth of such cells can be prevented, thereby controlling restenosis. This patent, however, does not address non-uniform irradiation, nor does it teach means for positioning and centering the radiation dose for effective irradiation on an essentially eccentric atheroma lesion region.
Treatment apparatus, such as a catheter or a wire has been disclosed. For example, U.S. Pat. No. 5,199,939 to Dake et al. discloses a radioactive catheter having a plurality of cylindrically shaped, radioactive pellets longitudinally spaced apart inside the lumen of the catheter. However, non-centering wire-carried radiation sources are sub-optimal in performance which has been disclosed by Dake et al. in U.S. Pat. No. 5,199,939 and Bradshaw in U.S. Pat. No. 5,643,171. Therefore, it would be highly desirable to provide a radiation delivery system that would assure that the source is somehow centered in the vessel for an essentially uniform atheroma lesion type or adjustably positioned about the center of the vessel for an eccentric atheroma lesion type.
Current balloon dilatation catheters employ a fixed or movable steerable guidewire which negotiates the serpentine coronary vasculature in an atraumatic fashion to provide a path for the passage of the balloon catheter. Apparatus for positioning a catheter distal tip is known and well practiced. U.S. Pat. No. 4,793,359 to Sharrow discloses a balloon near the tip of an angioplasty catheter for accurately establishing the position and orientation of the distal tip within an artery in response to the balloon dilation. The balloon comprises a distal wall portion substantially perpendicular to the central axis so as the catheter tip is placed in centered, coaxial relation to the balloon when the balloon is inflated. However, the atherosclerosis plaque is generally asymmetrically distributed around the artery wall. In an atherosclerotic artery, the balloon catheter as disclosed by Sharrow does not have an adjustable means for effectively positioning the distal tip.
U.S. Pat. No. 5,122,125 to Deuss discloses an angioplasty catheter having at least three radially protruding elements constructed of very soft material at its end portion so that a very great stability of the end portion is achieved against the surrounding vessel wall. However, the catheter still suffers the capability for adjusting its tip position and orientation for more effective irradiation therapy.
U.S. Pat. No. 5,179,961 to Littleford discloses a separate flexible tube having a peripherally expandable zone at the distal end of the tube so as to center and stabilize the flexible tube in place. A treatment catheter is then passed through the lumen of the flexible tube for tissue treatment. However, Littleford does not disclose a delivery catheter having an adjustable means for independently adjusting each of the expandable elements for effective positioning of the distal tip.
Aliahmad et al. in U.S. Pat. No. 5,295,960 discloses a catheter with balloon material or a membrane disposed interiorly of the catheter body in the inflation lumen so that the balloon material can be inflated to form at least one exterior balloon through holes of the catheter body at the end or the side of the catheter body. As disclosed, separate balloons formed from a single membrane can be deployed through respective openings circumferentially spaced or axially spaced. However, the balloon material or membrane does not have an adjustable means for independently adjusting each of the expandable balloons. The balloon material is not an integral part of the distal catheter body and may separate from the catheter body unexpectedly.
Inflation of conventional dilatation balloons completely blocks the artery, and thus interrupts distal coronary blood flow. Typical inflation time for radioactive treatment may range from 3 minutes to 60 minutes. Maintenance of coronary perfusion during dilation would greatly enhance the safety of coronary angioplasty, particularly in vessels serving large areas of myocardium. Therefore, it would be desirable for a radioactive treatment apparatus or delivery balloon catheter to provide for continuous blood flow (perfusion) past the stenotic region in the target coronary vessel.
U.S. Pat. No. 5,087,247 to Horn et al. and No. 5,295,995 to Kleiman disclose perfusion dilatation catheter having some clearance between the inflated balloon and the vessel wall so that continuous perfusion is maintained. Particularly, U.S. Pat. No. 5,295,995 shows an inflatable non-circular balloon, wherein the balloon tip has at least two substantially rounded axial protrusions or apices which, upon expansion of the balloon, come into apposition with the walls of the target vessel and form blood flow paths around the protrusions. The inflated balloon does not have adjustable means for effective positioning of the catheter tip for subsequent radiation treatment.
Numerous balloon catheters which afford varying degrees of coronary perfusion during balloon radioactive treatment have been described in the prior art. However, none of these catheters incorporate all of the necessary attributes mentioned above into a single device with adjustable centering capability at its distal tip portion.
Although a variety of procedures have been proposed for irradiating a treated vessel region, most of such procedures lack the ability to conveniently and effectively introduce a radiation source uniformly within the lesion vessel region preferably over a short treatment period. The xe2x80x9cuniformity of radiation source within the lesion vessel regionxe2x80x9d is referred to and defined in this invention as the appropriately proportional exposure of the radiation according to the need of the atheroma for radiation. In other words, more radiation shall be directed to the lesion region that needs more therapeutic dose.
Since majority of the atherosclerosis or the compressed atheroma is eccentric around the vessel wall, a radiation source should be adjusted to provide proportionally effective radiation dose according to the need of the site-specific atheroma for radiation treatment. This may also apply to the bifurcation or tortuous branch vessels. The radiation dose should be adjusted axially, radially, or a combination of axial and radial adjustment on a need basis for optimal tissue treatment.
Therefore, it would be desirable to provide methods and apparatus that would reduce or greatly eliminate such drawbacks of inefficient radiation so as to allow for the introduction and withdrawal of the radioactive source and provide for the proportionally effective dose to the lesion vessel region without suffering the above-discussed disadvantages.
In general, it is an object of the present invention to provide a device and methods for delivering radioactive dose adequately to treat essentially eccentric atheroma comprising positioning a radiation source close to the eccentric atheroma for a predetermined treatment period, wherein the positioning of the radiation source is adjustable. The modes for making the radiation source adjustable may include manual adjustment, auto-adjustment, continuous adjustment, rotatable adjustment, back-and-forth adjustment, programmed adjustment, and the like. Furthermore, the modes for making the radiation source adjustable may include a movable or rotatable radiation source during the radiation procedures.
The device may comprise a balloon catheter having adjustably centering capability and a treatment apparatus to be inserted within the catheter having radiation source for treating eccentric atheroma. It is another object of the present invention to provide a device and methods for positioning a radiation source axially adjustable, radially adjustable, combination of axially and radially adjustable, and the like with respect to the eccentric atheroma in a blood vessel. The adjustable centering process may be performed to a lesion region once or adjusted more than once for effective radiation therapy. It is still another object of the present invention to provide a device and methods for positioning a radiation source comprising a plurality of balloons disposed at a distal section of the device, wherein the plurality of balloons may be independently adjustable in inflation size, shape, diameter to stabilize the distal section of the device, such as a balloon catheter, with respect to the lesion region requiring radiation treatment.
In accordance with one embodiment of the invention, the eccentric atheroma is restenosis, preferably resulting from angioplasty, atherectomy, laser angioplasty, stenting, combination of angioplasty and stenting, or the like. Since atherosclerosis or arteriosclerosis is seldom uniformly distributed within the vessel wall, the eccentric atheroma in this invention includes essentially all types of atherosclerosis/arteriosclerosis before and/or after a procedure, such as angioplasty, stenting, atherectomy, surgery or the like.
In some cases, it may be desirable to maintain the radiation sources at a treatment region for an extended treatment period. For instance, in some cases it may be desirable to maintain the radioactive sources at a treatment site for up to about 20 minutes or more. It is one object of the present invention to provide perfusion schemes so that adequate blood flow is provided for flowing between any two of the balloon members.
In another preferred embodiment of the present invention, a radiation treatment system comprises a balloon catheter having adjustable centering capability, the balloon catheter comprising an elongated catheter shaft having a shaft distal end, a shaft proximal end, a shaft distal section, and a plurality of lumens between the shaft distal end and the shaft proximal end. A tubular centering structure is disposed at the shaft distal end, wherein the tubular centering structure comprises a plurality of balloon members that are radially expandable or inflatable, wherein each of said plurality of balloon members is independently adjustable in inflation size, shape, or diameter. Each of said plurality of balloon members is connected to and communicated to one of the plurality of lumens for balloon inflation using inflation fluid and deflation thereafter. The radiation treatment system further comprises a treatment apparatus slidably positioned inside one of the lumens, wherein the treatment apparatus comprises a radiation source.
In still another preferred embodiment, the tubular centering structure of the balloon catheter has an outer diameter essentially equivalent to an outer diameter of the catheter shaft. One of the lumens of the balloon catheter may be a lumen for passing or riding on a guide wire. The tubular centering structure of the balloon catheter may be made of material selected from elastomers consisting of polyurethane, silicone, blend of polyurethane and silicone, natural rubber, synthetic rubber, polyisoprene, polyisobutylene, nylon block copolymer, latex, polyethylene, copolyester, fluorocopolymer, SBR, and the like. The elongated catheter shaft of the balloon catheter may be made of material selected from the group consisting of polyethylene, polyimide, polypropylene, nylon, polyvinyl chloride, their mixture, and the like. The above-referred material is biocompatible and has been widely used for balloon and catheter body construction. Optionally, at least two of the balloon members of the tubular centering structure are positioned at different locations axially from one another.
The tubular centering structure or the shaft distal section of the balloon catheter may be imprinted with radiopaque ink for tracking exact location of the balloon catheter inside a patient. In another preferred embodiment, at least one radiopaque marker may be disposed at the shaft distal section or the distal element of the balloon catheter for tracking exact location of the balloon catheter inside a patient, wherein the distal element of the balloon catheter may be disposed distal to the tubular centering structure. In another preferred embodiment, the distal element has a lumen for inserting a guidewire.
In accordance with another embodiment of the invention, there is provided a method for treating restenosis of a lesion region of a patient comprising the steps of (a) inserting a balloon catheter through a body conduit to said lesion region of the patient, wherein the balloon catheter comprises a tubular centering structure disposed at a distal section of the balloon catheter, wherein the tubular centering structure comprises a plurality of balloon members that are independently radially expandable; (b) inflating each of the balloon members independently and adjustably in desired inflation size to stabilize the distal section of the balloon catheter with respect to the lesion region; (c) inserting a treatment apparatus inside a lumen of the balloon catheter, wherein the treatment apparatus comprises a radiation source; (d) positioning the radiation source at about the lesion region; (e) holding the radiation source for a predetermined treatment period for treating restenosis; and (f) withdrawing the treatment apparatus.
To place the radiation sources in apposition with the vessel wall in a desired pattern, the invention employs a radially expandable tubular centering structure having a plurality of individually adjustable balloon members. The adjustable balloon member is radially expandable. Exemplary radially expandable balloon members of the tubular centering structure may comprise semi-compliant balloon and compliant balloon, such as a conventional angioplasty balloon, elastomeric balloons, and the like. The elastomeric balloon may preferably be constructed of materials selected from the group consisting of polyurethane, silicone, blend of polyurethane and silicone, natural rubber, synthetic rubber, polyisoprene, polyisobutylene, nylon block copolymer, latex, polyethylene, copolyester, fluorocopolymer, SBR, and the like. The semi-compliant balloon may preferably be constructed of materials selected from the group consisting of polyethylene, nylon or the like.
The radiation sources may preferably emit gamma (xcex3) radiation, beta (xcex2) radiation, or combination of gamma and beta radiation. Exemplary of radiation sources include 90Strontium, 90Yttrium, 125Iodine, 192Iridium and the like. The radiation sources may preferably comprise a plurality of discrete elements, such as seeds, elongate strips, ribbons, wires, ribs and the like. The effective dose to inhibit smooth muscle cell hyperplasia and the resulting restenosis is approximately a few thousand rads, preferably 1,000 to 5,000 rads. For a given source, the intensity of the radiation drops rapidly as a function of the distance from the source. Accordingly, if the source is not held reasonably near the lesion region, for a given treatment period, the portion of the vessel wall may not receive adequate dose of radiation, while the portion of the non-lesion region may receive more than prescribed dose. Overdosing of a section of blood vessel may cause arterial necrosis, inflammation and hemorrhage. Underdosing may result in no inhibition of smooth muscle cell proliferation or even exacerbation of the hyperplasia and resulting restenosis.
In one preferred embodiment, a method of delivering radiation dose comprises disposing the radiation source at a tip portion of a treatment apparatus, wherein the treatment apparatus is a wire, a catheter, a combination of wire and catheter, and the like. The tip portion of the treatment apparatus may optionally be adjustable, wherein the modes for making the radiation source adjustable may include manual adjustment, auto-adjustment, continuous adjustment, rotatable adjustment, back-and-forth adjustment, programmed adjustment, and the like.